How do I change the first ring option to the desk phone and have the cellphone/smartphone option as the rollover?

Schopke,

What you would have to do is select your deskphone as the first option in Call Handling & Forwarding, then add/select your cell phone as the second option and have the calls ring sequentially.

CAVEAT: If you select this way of doing it, your cell phone calls will go to your cellphone and NOT to the RingCentral Mobile application. You will lose the functionality of the RC Mobile app.

There currently is no configuration option to have the Desk phone ring first and then ring the Windows Desktop/Smartphone (RC Mobile app) as a second option.